<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      .ces {
        width: 500px;
        display: flex;
        margin: 0 auto;
      }
      li {
        width: 100px;
        height: 50px;
        background-color: antiquewhite;
        margin: 3px;
      }
      @media (max-width: 750px) {
        .hengXiang {
          flex-direction: column;
        }
        .height {
          height: 200px !important;
        }
      }
    </style>
  </head>
  <body>
    <ul class="ces hengXiang">
      <li></li>
      <li></li>
      <li></li>
      <li></li>
    </ul>
  </body>
</html>
